1. Field of the Invention
The present invention relates to a mobile communication system and a control method thereof and a radio network controller and a base station used for the same, and more in particular, it relates to a setting up control system of a unidirectional dedicated channel between the radio network controller and the base station.
2. Description of the Prior Art
In recent years, in a 3GPP (Third Generation Partnership Project), a high speed downlink packet transmission technology has been standardized. This technology is referred to as HSDPA (High Speed Downlink Packet Access), and the channel used in this technology is referred to as a HS-DSCH (High Speed Downlink Shared Channel).
According to the specification of the present 3GPP, there exists a mechanism, wherein dedicated channels are set up in a pair for the uplink and the downlink in the section between a network and a mobile communication terminal (referred to as UE: User Equipment), and RLC AM (Radio Link Control Acknowledged Mode) is executed between the network and the UE. The dedicated channel for the UE is referred to as a DCH (Dedicated Channel) (cf., Japanese Patent Laid-Open No. 2001-186550).
According to the RLC AM, for example, when the UE correctly receives a downlink data, the UE notifies to the network that the data is correctly received by using the uplink channel set up in a pair with the downlink channel, and when the UE does not correctly receive the downlink data, the UE notifies to the network that the data is not correctly received by using the uplink channel. In the later case, the network re-transmits the data not correctly received by the UE.
As shown in FIG. 3, the network comprises a CN (Core Network) 1, an RNC (Radio Network Controller) 2, and a Node B (Radio Base Station) 3, and the RNC 2 has an AM unit 201, which is a function to realize the above described RLC AM, and an UE 4 has also an AM unit 401 corresponding to the AM unit 201. As described above, in the 3GPP, this AM is referred to as the RLC AM.
When the high speed packet transmission channel (HS-DSCH) is set up in a downlink (DL), and moreover, the RLC AM is used, it is necessary to set up an uplink (UL) DCH to be a pair with the HS-DSCH. To set up the HS-DSCH, it is necessary that the UE 4 transitions into a RRC (Radio Resource Control) state, referred to as a Cell-DCH, and in the state of the Cell-DCH, the DCH is set up as a channel for a communication line.